Selective dissolving

Leaching. Extracting a soluble metallic compound from an ore by selectively dissolving it in a suitable solvent. The solvent is usually recovered by precipitation of the metal or by other methods. 

An isolated flagellum will continue to bend actively, indicating that this function is linked to its intrinsic structure. Treatment of cilia from the protozoan Tetra-hymena with the proteolytic enzyme trypsin selectively dissolves the nexin links and radial spokes but leaves unaffected the microtubules and dynein arms. If such a preparation is treated with a small amount of ATP, the loosened microtubule doublets slide against each other and through longitudinal overlap, extend for a distance that is up to nine times the original length of the cilium (Warner and Mitchell, 1981). 

If only nonprecious atoms (e.g., Co or Fe) were selectively dissolved from the alloy surface, the roughness of the resulting Pt surface layer would be increased with the number of sweeps. However, as seen in Fig. 10.2a, the value of AQ (a measure of the electrochemical surface area) rather decreases gradually and reaches a steady value. 

The purification obtained in electrorefining is based on the selectivity provided by the process itself. Electrorefining may, in principle, be carried out along two different paths, depending on the nature of the impurities to be removed. Either the impure metal forms the anode and the pure metal is concentrated in the cathode, or the impurities are selectively dissolved from the anode so that the purity of the metal constituting it increases. Although literature records electrorefining processes based on both these approaches, the former seems to dominate in commercial practice. 

Figure 69 presents typical NSE spectra of such a system [174]. They were obtained from a 2% diblock copolymer (perdeuterated PS and protonated PI blocks) d-n-decane solution. The molecular masses Mw of PS and PI were 10000 and 7500 g/mol, respectively. The solvent selectively dissolves PI but not PS. In... 

A cationic complex, formed in situ from 5 and [Rh(COD)2]OTf, was also active in biphasic hydrogenation [14]. No preference for the fluorous phase was found for ligands containing only one perfluoroalkyl tail, but neutral and cationic complexes, containing mono- and bidentate 4a or 5, respectively, were selectively dissolved in the fluorous phase. No leaching and recycling studies were performed. 

Skeletal (Raney ) catalysts are made by a very simple technique. An alloy of two metals in roughly equal proportions, where one metal is the desired catalytic material, and the other is dissolvable in hydroxide, is first made. This alloy is crashed and leached in concentrated hydroxide solution. The soluble metal selectively dissolves, leaving behind a highly porous spongelike structure of the desired catalytic metal. Catalysts formed by this technique show high activity and selectivity, and have found wide use in industry, particularly for hydrogenation and dehydrogenation reactions. 

In Section 2.5, we described separation procedures in which analytes are extracted from solid samples via contact with liquid solvents that selectively dissolve the analyte and leave other components undissolved or unextracted. There are several methods by which analytes can be extracted from liquid matrices as well. 

Separation can also be accomplished by solvent extraction, adsorption, and crystallization. Solvent extraction is accomplished by selectively dissolving certain hydrocarbon components. Adsorption is similar to solvent extraction but uses a solid to separate out various components selectively based on their tendency to adhere to the surface of the solid adsorbent. Crystallization uses the differing melting points of the components during cooling, which causes some of its compounds to solidify or crystallize, and separate out of the liquid. 

A solution of ethanol-water with diluted H2SO4 selectively dissolves the lignin and hemicellulose at 180-200 °C [55]. The resulting purified cellulose can subsequently be fermented to ethanol at high yield. Copersucar and Dedinin are developing a process for bagasse-ethanol that is based on such a pre-treatment of the bagasse [56]. 

There are certain compounds that have the remarkable characteristic of being able to selectively dissolve some compounds, while at the same time ignoring others. A familiar example might be to take a spoonful of table salt and drop it into a half a glass of paint thinner. The salt sinks to the bottom of the glass. Mix it, shake it, and it still settles down to the bottom because it wont dissolve in paint thinner. Having observed that, it would be tough to get that salt completely separated from the paint thinner. 

Scrubber. A packed column or fractionator used to separate components of a gas stream. The gas vapor passes up the column as a liquid descends. The liquid will selectively dissolve some of the components of the gas... 

Figure 17. A schematic representation of positive resist action in diazonaphthoquinone-novolac resists. Photolysis of the sensitizer inhibitor) produces acid which allows the exposed areas of the resist to be selectively dissolved (developed) in aqueous base.

Selectivity, dissolving to a large extent one of the key components without dissolving other components to any large extent... 

The chemical properties of solvents have obviously a strong bearing on their applicability for various purposes. The solvents function by selectively dissolving desired solutes, by remaining inactive in the chemical reactions undergone by the solutes, and by solvating (selectively), reactants, transition-state intermediates, and products (Marcus, 1998a). 

A unique liquid-phase isomerization to produce m-xylene in the presence of HF-BF3 was developed by Mitsubishi288 on the basis of earlier work by Lien and McCaulay,83 who found that m-xylene forms the most stable a complex in HF-BF3 at low temperature. This complex selectively dissolves in the acid phase, allowing easy separation from the less stable other two isomers. The complex then is decomposed to produce pure m-xylene. 

Separation of ions can be accomplished by selectively dissolving a mixture of precipitates, or by selectively precipitating a mixture of ions. The following problems illustrate this. 

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